[1] Inkosi Albert Luthuli Cent Hosp, Dept Anaesthet, Durban, South Africa
[2] Univ KwaZulu Natal, Nelson R Mandela Sch Med, Durban, South Africa
[3] Univ Toronto, Sunnybrook Hlth Sci Ctr, Dept Anesthesia, Toronto, ON, Canada
[4] Greys Hosp, Dept Anaesthet, Pietermaritzburg, South Africa
[5] Cleveland Clin, Dept Outcomes Res, Cleveland, OH 44106 USA